The present invention relates to a fiber reinforced drive shaft, particularly a universal-joint shaft for motor vehicles, such as a Cardan shaft or the like.
Fiber reinforced drive shafts of the above-mentioned general type are known in the art. The German Offenlegungsschrift No. 2,851,292 describes, for example, the construction and method of manufacturing of a fiber reinforced Cardan shaft. It is provided with metallic end pieces each including a yoke part and an anchoring part of one piece with one another. For manufacturing the shaft, the end pieces are pulled onto the ends of a prefabricated tubular one-way mandrel, and after this in cooperation with the one-way mandrel located therebetween are enveloped with fiber reinforced synthetic plastic material. After hardening and vulcanization, the end pieces are thereby fixedly anchored, so that they form an unseparable unit with the thus-produced main part. Each of the yoke portions of the Cardan shafts can be assembled with the respective connecting yoke part with the aid of a transverse pin, so as to form a complete Cardan joint. The Cardan joint of the above-described construction is characterized by improved swinging condition as well as a smaller weight, as compared with conventional universal joints, particularly Cardan joints of steel.
Another drive shaft has a shaft part composed of a synthetic plastic matrix with embedded high strength fibers or fiber bundles which form a plurality of wound layers with windings of the inner and outer layers being helical and having a low pitch, but a pitch angle about 30.degree.-60.degree. of intermediate layers and with the windings of successive intermediate layers crossing one another. In this drive shaft, the projecting part of each end piece is formed as a ring section which is of one piece with a sleeve section having a greater outer diameter and an identical inner diameter, wherein the ring section has an inner end face bonded with the fibers or fiber bundles embedded in the synthetic plastic matrix. The end portions of the shaft part project from the fixedly connected end pieces, and the ring sections of the end pieces has end faces which form a stop and an end abutment for the end portions of the shaft part. Thereby, the thus formed end faces protect the shaft part against ambient influences.
It has been shown in practice that the above-described construction of the universal-joint shaft provides for excellent results. The sleeve section of each end piece has the identical inner diameter as their main section and extends into the interior of the shaft part with a reduced cross-section. The sleeve section is provided with an annular groove in the region of transition between the sleeve section and the ring section. When the end pieces are designed in the above-mentioned manner, there are certain difficulties in bringing of fibers or fiber bundles with a pitch angle between 30.degree. and 60.degree. and with the windings of successive layers crossing one another, onto the outer surface of the end pieces of metal to be connected therewith. During continuous winding of the shaft part, a reverse of the winding direction in the end regions of the shaft part is necessary when continuous fibers or fiber bundles must be wound. This is desirable for optimum strength of the ends of the connecting tubular parts and facilitation of the winding process. In this case, however, it is impossible to avoid the reverse loops of each fiber winding during the winding process, until an opposite displacement. The accidental position of the turning point of the fibers or fiber bundles can lead to an undesirable fiber structure at the ends of the shaft part which, in turn can undesirably affect optimum mechanical strength of the shaft in these regions.